FIELD OF THE INVENTION
The invention relates to a contactless proximity switch for detecting at least one predefined spacing between a first part and a second part mounted in a fashion capable of movement with respect thereto.
Prior art contactless proximity switches based on magnetic sensors utilize a permanent magnet in a first part and a reed relay in a second part. When a specific spacing from the permanent magnet is reached, then the reed relay switches because of a change in magnetic flux density in the relay. The detection of a change in flux density by means of a reed relay is, however, very susceptible to interference with respect to external magnetic interference fields in the environment of the magnetic system, and with respect to vibrations.
A proximity switch with a magnetoresistive sensor that is capable of moving relative to a permanent magnet is known from August Petersen: "The Magnetoresistive Sensor"; Electronic Components and Applications, Vol. 8, No. 4, pp. 222-39, 235. It is necessary in that proximity switch, to select a very high switching level in order to reduce the interference susceptibility with respect to external magnetic interference fields.